/*
 * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1997 by Silicon Graphics.  All rights reserved.
 * Copyright (c) 2009-2022 Ivan Maidanski
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose, provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */

#include "private/gc_priv.h"

/*
 * This is incredibly OS specific code for tracking down data sections in
 * dynamic libraries.  There appears to be no way of doing this quickly
 * without groveling through undocumented data structures.  We would argue
 * that this is a bug in the design of the dlopen interface.  THIS CODE
 * MAY BREAK IN FUTURE OS RELEASES.  If this matters to you, don't hesitate
 * to let your vendor know ...
 *
 * None of this is safe with dlclose and incremental collection.
 * But then not much of anything is safe in the presence of dlclose.
 */

/* BTL: avoid circular redefinition of dlopen if GC_SOLARIS_THREADS defined */
#undef GC_MUST_RESTORE_REDEFINED_DLOPEN
#if defined(GC_PTHREADS) && !defined(GC_NO_DLOPEN) \
    && !defined(GC_NO_THREAD_REDIRECTS) && !defined(GC_USE_LD_WRAP)
  /* To support threads in Solaris, gc.h interposes on dlopen by        */
  /* defining "dlopen" to be "GC_dlopen", which is implemented below.   */
  /* However, both GC_FirstDLOpenedLinkMap() and GC_dlopen() use the    */
  /* real system dlopen() in their implementation. We first remove      */
  /* gc.h's dlopen definition and restore it later, after GC_dlopen().  */
# undef dlopen
# define GC_MUST_RESTORE_REDEFINED_DLOPEN
#endif /* !GC_NO_DLOPEN */

#if defined(SOLARISDL) && defined(THREADS) && !defined(PCR) \
    && !defined(GC_SOLARIS_THREADS) && !defined(CPPCHECK)
#  error Fix mutual exclusion with dlopen
#endif

/* A user-supplied routine (custom filter) that might be called to      */
/* determine whether a DSO really needs to be scanned by the GC.        */
/* 0 means no filter installed.  May be unused on some platforms.       */
/* FIXME: Add filter support for more platforms.                        */
STATIC GC_has_static_roots_func GC_has_static_roots = 0;

#if defined(DYNAMIC_LOADING) && !defined(PCR) || defined(ANY_MSWIN)

#if !(defined(CPPCHECK) || defined(AIX) || defined(ANY_MSWIN) \
      || defined(DARWIN) || defined(DGUX) || defined(IRIX5) \
      || defined(HAIKU) || defined(HPUX) || defined(HURD) \
      || defined(NACL) || defined(SCO_ELF) || defined(SOLARISDL) \
      || ((defined(ANY_BSD) || defined(LINUX)) && defined(__ELF__)) \
      || (defined(ALPHA) && defined(OSF1)) \
      || (defined(OPENBSD) && defined(M68K)))
# error We only know how to find data segments of dynamic libraries for above.
# error Additional SVR4 variants might not be too hard to add.
#endif

#if defined(DARWIN) && !defined(USE_DYLD_TO_BIND) \
    && !defined(NO_DYLD_BIND_FULLY_IMAGE)
# include <dlfcn.h>
#endif

#ifdef SOLARISDL
#   include <sys/elf.h>
#   include <dlfcn.h>
#   include <link.h>
#endif

#if defined(NETBSD)
#   include <sys/param.h>
#   include <dlfcn.h>
#   include <machine/elf_machdep.h>
#   define ELFSIZE ARCH_ELFSIZE
#endif

#if defined(OPENBSD)
# include <sys/param.h>
# if (OpenBSD >= 200519) && !defined(HAVE_DL_ITERATE_PHDR)
#   define HAVE_DL_ITERATE_PHDR
# endif
#endif /* OPENBSD */

#if defined(DGUX) || defined(HURD) || defined(NACL) || defined(SCO_ELF) \
    || ((defined(ANY_BSD) || defined(LINUX)) && defined(__ELF__))
# include <stddef.h>
# if !defined(OPENBSD) && !defined(HOST_ANDROID)
    /* OpenBSD does not have elf.h file; link.h below is sufficient.    */
    /* Exclude Android because linker.h below includes its own version. */
#   include <elf.h>
# endif
# ifdef HOST_ANDROID
    /* If you don't need the "dynamic loading" feature, you may build   */
    /* the collector with -D IGNORE_DYNAMIC_LOADING.                    */
#   ifdef BIONIC_ELFDATA_REDEF_BUG
      /* Workaround a problem in Bionic (as of Android 4.2) which has   */
      /* mismatching ELF_DATA definitions in sys/exec_elf.h and         */
      /* asm/elf.h included from linker.h file (similar to EM_ALPHA).   */
#     include <asm/elf.h>
#     include <linux/elf-em.h>
#     undef ELF_DATA
#     undef EM_ALPHA
#   endif
#   include <link.h>
#   if !defined(GC_DONT_DEFINE_LINK_MAP) && !(__ANDROID_API__ >= 21)
      /* link_map and r_debug are defined in link.h of NDK r10+.        */
      /* bionic/linker/linker.h defines them too but the header         */
      /* itself is a C++ one starting from Android 4.3.                 */
      struct link_map {
        uintptr_t l_addr;
        char* l_name;
        uintptr_t l_ld;
        struct link_map* l_next;
        struct link_map* l_prev;
      };
      struct r_debug {
        int32_t r_version;
        struct link_map* r_map;
        void (*r_brk)(void);
        int32_t r_state;
        uintptr_t r_ldbase;
      };
#   endif
# else
    EXTERN_C_BEGIN      /* Workaround missing extern "C" around _DYNAMIC */
                        /* symbol in link.h of some Linux hosts.         */
#   include <link.h>
    EXTERN_C_END
# endif
#endif

/* Newer versions of GNU/Linux define this macro.  We
 * define it similarly for any ELF systems that don't.  */
# ifndef ElfW
#   if defined(FREEBSD)
#     if __ELF_WORD_SIZE == 32
#       define ElfW(type) Elf32_##type
#     else
#       define ElfW(type) Elf64_##type
#     endif
#   elif defined(NETBSD) || defined(OPENBSD)
#     if ELFSIZE == 32
#       define ElfW(type) Elf32_##type
#     elif ELFSIZE == 64
#       define ElfW(type) Elf64_##type
#     else
#       error Missing ELFSIZE define
#     endif
#   else
#     if !defined(ELF_CLASS) || ELF_CLASS == ELFCLASS32
#       define ElfW(type) Elf32_##type
#     else
#       define ElfW(type) Elf64_##type
#     endif
#   endif
# endif

#if defined(SOLARISDL) && !defined(USE_PROC_FOR_LIBRARIES)

  EXTERN_C_BEGIN
  extern ElfW(Dyn) _DYNAMIC;
  EXTERN_C_END

  STATIC struct link_map *
  GC_FirstDLOpenedLinkMap(void)
  {
    ElfW(Dyn) *dp;
    static struct link_map * cachedResult = 0;
    static ElfW(Dyn) *dynStructureAddr = 0;
                /* BTL: added to avoid Solaris 5.3 ld.so _DYNAMIC bug   */

#   ifdef SUNOS53_SHARED_LIB
        /* BTL: Avoid the Solaris 5.3 bug that _DYNAMIC isn't being set */
        /* up properly in dynamically linked .so's. This means we have  */
        /* to use its value in the set of original object files loaded  */
        /* at program startup.                                          */
        if (0 == dynStructureAddr) {
          void *startupSyms = dlopen(0, RTLD_LAZY);

          dynStructureAddr = (ElfW(Dyn) *)dlsym(startupSyms, "_DYNAMIC");
          /* Note: dlclose() is not called intentionally. */
        }
#   else
        dynStructureAddr = &_DYNAMIC;
#   endif

    if (0 == COVERT_DATAFLOW(ADDR(dynStructureAddr))) {
        /* _DYNAMIC symbol not resolved. */
        return NULL;
    }
    if (cachedResult == 0) {
        int tag;

        for (dp = (ElfW(Dyn) *)&_DYNAMIC; (tag = dp->d_tag) != 0; dp++) {
            if (tag == DT_DEBUG) {
                const struct r_debug *rd = (struct r_debug *)dp->d_un.d_ptr;
                if (rd != NULL) {
                    const struct link_map *lm = rd->r_map;
                    if (lm != NULL)
                        cachedResult = lm->l_next; /* might be NULL */
                }
                break;
            }
        }
    }
    return cachedResult;
  }

  GC_INNER void GC_register_dynamic_libraries(void)
  {
    struct link_map *lm;

    GC_ASSERT(I_HOLD_LOCK());
    for (lm = GC_FirstDLOpenedLinkMap(); lm != 0; lm = lm->l_next) {
        ElfW(Ehdr) * e;
        ElfW(Phdr) * p;
        unsigned long offset;
        char * start;
        int i;

        e = (ElfW(Ehdr) *)lm->l_addr;
        p = ((ElfW(Phdr) *)(((char *)(e)) + e->e_phoff));
        offset = ((unsigned long)(lm->l_addr));
        for (i = 0; i < (int)e->e_phnum; i++, p++) {
          switch (p->p_type) {
            case PT_LOAD:
              if (!(p->p_flags & PF_W)) break;
              start = (char *)(p->p_vaddr) + offset;
              GC_add_roots_inner(start, start + p->p_memsz, TRUE);
              break;
            default:
              break;
          }
        }
    }
  }

#endif /* SOLARISDL && !USE_PROC_FOR_LIBRARIES */

#if defined(DGUX) || defined(HURD) || defined(NACL) || defined(SCO_ELF) \
    || ((defined(ANY_BSD) || defined(LINUX)) && defined(__ELF__))

#ifdef USE_PROC_FOR_LIBRARIES

#include <string.h>

#include <sys/stat.h>
#include <fcntl.h>

#define MAPS_BUF_SIZE (32*1024)

/* Sort an array of HeapSects by start address.                         */
/* Unfortunately at least some versions of                              */
/* Linux qsort end up calling malloc by way of sysconf, and hence can't */
/* be used in the collector.  Hence we roll our own.  Should be         */
/* reasonably fast if the array is already mostly sorted, as we expect  */
/* it to be.                                                            */
static void sort_heap_sects(struct HeapSect *base, size_t number_of_elements)
{
    signed_word n = (signed_word)number_of_elements;
    signed_word nsorted = 1;

    while (nsorted < n) {
      signed_word i;

      while (nsorted < n
             && ADDR_LT(base[nsorted-1].hs_start, base[nsorted].hs_start)) {
        ++nsorted;
      }
      if (nsorted == n) break;
      GC_ASSERT(ADDR_LT(base[nsorted].hs_start, base[nsorted-1].hs_start));
      for (i = nsorted - 1;
           i >= 0 && ADDR_LT(base[i+1].hs_start, base[i].hs_start); --i) {
        struct HeapSect tmp = base[i];

        base[i] = base[i+1];
        base[i+1] = tmp;
      }
      GC_ASSERT(ADDR_LT(base[nsorted-1].hs_start, base[nsorted].hs_start));
      ++nsorted;
    }
}

STATIC void GC_register_map_entries(const char *maps)
{
    const char *prot, *path;
    ptr_t start, end;
    ptr_t least_ha, greatest_ha;
    unsigned maj_dev;
    unsigned i;

    GC_ASSERT(I_HOLD_LOCK());
    sort_heap_sects(GC_our_memory, GC_n_memory);
    least_ha = GC_our_memory[0].hs_start;
    greatest_ha = GC_our_memory[GC_n_memory-1].hs_start
                  + GC_our_memory[GC_n_memory-1].hs_bytes;

    for (;;) {
        maps = GC_parse_map_entry(maps, &start, &end, &prot, &maj_dev, &path);
        if (NULL == maps) break;

        if (prot[1] == 'w') {
            /* This is a writable mapping.  Add it to           */
            /* the root set unless it is already otherwise      */
            /* accounted for.                                   */
#           ifndef THREADS
              if (ADDR_GE(GC_stackbottom, start)
                  && ADDR_GE(end, GC_stackbottom)) {
                /* Stack mapping; discard it.   */
                continue;
              }
#           endif
#           if defined(E2K) && defined(__ptr64__)
              /* TODO: avoid hard-coded addresses */
              if (ADDR(start) == 0xc2fffffff000UL
                  && ADDR(end) == 0xc30000000000UL && path[0] == '\n')
                continue; /* discard some special mapping */
#           endif
            if (path[0] == '[' && strncmp(path + 1, "heap]", 5) != 0)
              continue; /* discard if a pseudo-path unless "[heap]" */

#           ifdef THREADS
              /* This may fail, since a thread may already be           */
              /* unregistered, but its thread stack may still be there. */
              /* That can fail because the stack may disappear while    */
              /* we're marking.  Thus the marker is, and has to be      */
              /* prepared to recover from segmentation faults.          */

              if (GC_segment_is_thread_stack(start, end)) continue;

              /* FIXME: NPTL squirrels                                  */
              /* away pointers in pieces of the stack segment that we   */
              /* don't scan.  We work around this                       */
              /* by treating anything allocated by libpthread as        */
              /* uncollectible, as we do in some other cases.           */
              /* A specifically identified problem is that              */
              /* thread stacks contain pointers to dynamic thread       */
              /* vectors, which may be reused due to thread caching.    */
              /* They may not be marked if the thread is still live.    */
              /* This specific instance should be addressed by          */
              /* INCLUDE_LINUX_THREAD_DESCR, but that doesn't quite     */
              /* seem to suffice.                                       */
              /* We currently trace entire thread stacks, if they are   */
              /* are currently cached but unused.  This is              */
              /* very suboptimal for performance reasons.               */
#           endif
            /* We no longer exclude the main data segment.              */
            if (ADDR_GE(least_ha, end) || ADDR_GE(start, greatest_ha)) {
              /* The easy case; just trace the entire segment.  */
              GC_add_roots_inner(start, end, TRUE);
              continue;
            }
            /* Add sections that don't belong to us. */
              i = 0;
              while (ADDR_LT(GC_our_memory[i].hs_start
                             + GC_our_memory[i].hs_bytes, start)) {
                ++i;
              }
              GC_ASSERT(i < GC_n_memory);
              if (ADDR_GE(start, GC_our_memory[i].hs_start)) {
                start = GC_our_memory[i].hs_start + GC_our_memory[i].hs_bytes;
                ++i;
              }
              for (; i < GC_n_memory && ADDR_LT(start, end)
                     && ADDR_LT(GC_our_memory[i].hs_start, end); ++i) {
                if (ADDR_LT(start, GC_our_memory[i].hs_start))
                  GC_add_roots_inner(start,
                                     GC_our_memory[i].hs_start, TRUE);
                start = GC_our_memory[i].hs_start
                        + GC_our_memory[i].hs_bytes;
              }
              if (ADDR_LT(start, end))
                GC_add_roots_inner(start, end, TRUE);
        } else if (prot[0] == '-' && prot[1] == '-' && prot[2] == '-') {
            /* Even roots added statically might disappear partially    */
            /* (e.g. the roots added by INCLUDE_LINUX_THREAD_DESCR).    */
            GC_remove_roots_subregion(start, end);
        }
    }
}

GC_INNER void GC_register_dynamic_libraries(void)
{
    GC_register_map_entries(GC_get_maps());
}

/* We now take care of the main data segment ourselves: */
GC_INNER GC_bool GC_register_main_static_data(void)
{
    return FALSE;
}

# define HAVE_REGISTER_MAIN_STATIC_DATA

#else /* !USE_PROC_FOR_LIBRARIES */

/* The following is the preferred way to walk dynamic libraries */
/* for glibc 2.2.4+.  Unfortunately, it doesn't work for older  */
/* versions.  Thanks to Jakub Jelinek for most of the code.     */

#if GC_GLIBC_PREREQ(2, 3) || defined(HOST_ANDROID)
                        /* Are others OK here, too? */
# ifndef HAVE_DL_ITERATE_PHDR
#   define HAVE_DL_ITERATE_PHDR
# endif
# ifdef HOST_ANDROID
    /* Android headers might have no such definition for some targets.  */
    EXTERN_C_BEGIN
    extern int dl_iterate_phdr(int (*cb)(struct dl_phdr_info *,
                                         size_t, void *),
                               void *data);
    EXTERN_C_END
# endif
#endif /* __GLIBC__ >= 2 || HOST_ANDROID */

#if defined(__DragonFly__) || defined(__FreeBSD_kernel__) \
    || (defined(FREEBSD) && __FreeBSD__ >= 7)
  /* On the FreeBSD system, any target system at major version 7 shall   */
  /* have dl_iterate_phdr; therefore, we need not make it weak as below. */
# ifndef HAVE_DL_ITERATE_PHDR
#   define HAVE_DL_ITERATE_PHDR
# endif
# define DL_ITERATE_PHDR_STRONG
#elif defined(HAVE_DL_ITERATE_PHDR)
  /* We have the header files for a glibc that includes dl_iterate_phdr.*/
  /* It may still not be available in the library on the target system. */
  /* Thus we also treat it as a weak symbol.                            */
  EXTERN_C_BEGIN
# pragma weak dl_iterate_phdr
  EXTERN_C_END
#endif

#if defined(HAVE_DL_ITERATE_PHDR)

# ifdef PT_GNU_RELRO
/* Instead of registering PT_LOAD sections directly, we keep them       */
/* in a temporary list, and filter them by excluding PT_GNU_RELRO       */
/* segments.  Processing PT_GNU_RELRO sections with                     */
/* GC_exclude_static_roots instead would be superficially cleaner.  But */
/* it runs into trouble if a client registers an overlapping segment,   */
/* which unfortunately seems quite possible.                            */

#   define MAX_LOAD_SEGS MAX_ROOT_SETS

    static struct load_segment {
      ptr_t start;
      ptr_t end;
      /* Room for a second segment if we remove a RELRO segment */
      /* from the middle.                                       */
      ptr_t start2;
      ptr_t end2;
    } load_segs[MAX_LOAD_SEGS];

    static int n_load_segs;
    static GC_bool load_segs_overflow;
# endif /* PT_GNU_RELRO */

STATIC int GC_register_dynlib_callback(struct dl_phdr_info * info,
                                       size_t size, void * ptr)
{
  const ElfW(Phdr) * p;
  ptr_t start, end;
  int i;

  GC_ASSERT(I_HOLD_LOCK());
  /* Make sure struct dl_phdr_info is at least as big as we need.  */
  if (size < offsetof(struct dl_phdr_info, dlpi_phnum)
                + sizeof(info->dlpi_phnum))
    return -1;

  p = info->dlpi_phdr;
  for (i = 0; i < (int)info->dlpi_phnum; i++, p++) {
    if (p->p_type == PT_LOAD) {
      GC_has_static_roots_func callback = GC_has_static_roots;
      if ((p->p_flags & PF_W) == 0) continue;

      start = (ptr_t)p->p_vaddr + info->dlpi_addr;
      end = start + p->p_memsz;
      if (callback != 0 && !callback(info->dlpi_name, start, p->p_memsz))
        continue;
#     ifdef PT_GNU_RELRO
#       if CPP_PTRSZ >= 64
          /* TODO: GC_push_all eventually does the correct          */
          /* rounding to the next multiple of ALIGNMENT, so, most   */
          /* probably, we should remove the corresponding assertion */
          /* check in GC_add_roots_inner along with this code line. */
          /* start pointer value may require aligning.              */
          start = PTR_ALIGN_DOWN(start, sizeof(ptr_t));
#       endif
        if (n_load_segs >= MAX_LOAD_SEGS) {
          if (!load_segs_overflow) {
            WARN("Too many PT_LOAD segments;"
                 " registering as roots directly...\n", 0);
            load_segs_overflow = TRUE;
          }
          GC_add_roots_inner(start, end, TRUE);
        } else {
          load_segs[n_load_segs].start = start;
          load_segs[n_load_segs].end = end;
          load_segs[n_load_segs].start2 = NULL;
          load_segs[n_load_segs].end2 = NULL;
          ++n_load_segs;
        }
#     else
        GC_add_roots_inner(start, end, TRUE);
#     endif /* !PT_GNU_RELRO */
    }
  }

# ifdef PT_GNU_RELRO
    p = info->dlpi_phdr;
    for (i = 0; i < (int)info->dlpi_phnum; i++, p++) {
      if (p->p_type == PT_GNU_RELRO) {
        /* This entry is known to be constant and will eventually be    */
        /* remapped as read-only.  However, the address range covered   */
        /* by this entry is typically a subset of a previously          */
        /* encountered "LOAD" segment, so we need to exclude it.        */
        int j;

        start = (ptr_t)p->p_vaddr + info->dlpi_addr;
        end = start + p->p_memsz;
        for (j = n_load_segs; --j >= 0; ) {
          if (ADDR_INSIDE(start, load_segs[j].start, load_segs[j].end)) {
            if (load_segs[j].start2 != NULL) {
              WARN("More than one GNU_RELRO segment per load one\n", 0);
            } else {
              GC_ASSERT(ADDR_GE(PTR_ALIGN_UP(load_segs[j].end, GC_page_size),
                                end));
              /* Remove from the existing load segment. */
              load_segs[j].end2 = load_segs[j].end;
              load_segs[j].end = start;
              load_segs[j].start2 = end;
              /* Note that start2 may be greater than end2 because of   */
              /* p->p_memsz value multiple of page size.                */
            }
            break;
          }
          if (0 == j && 0 == GC_has_static_roots)
            WARN("Failed to find PT_GNU_RELRO segment"
                 " inside PT_LOAD region\n", 0);
            /* No warning reported in case of the callback is present   */
            /* because most likely the segment has been excluded.       */
        }
      }
    }
# endif

  *(int *)ptr = 1;     /* Signal that we were called */
  return 0;
}

/* Do we need to separately register the main static data segment? */
GC_INNER GC_bool GC_register_main_static_data(void)
{
# if defined(DL_ITERATE_PHDR_STRONG) && !defined(CPPCHECK)
    /* If dl_iterate_phdr is not a weak symbol then don't test against  */
    /* zero (otherwise a compiler might issue a warning).               */
    return FALSE;
# else
    return 0 == COVERT_DATAFLOW(ADDR(dl_iterate_phdr));
# endif
}

/* Return TRUE if we succeed, FALSE if dl_iterate_phdr wasn't there. */
STATIC GC_bool GC_register_dynamic_libraries_dl_iterate_phdr(void)
{
  int did_something;

  GC_ASSERT(I_HOLD_LOCK());
  if (GC_register_main_static_data())
    return FALSE;

# ifdef PT_GNU_RELRO
    {
      static GC_bool excluded_segs = FALSE;
      n_load_segs = 0;
      load_segs_overflow = FALSE;
      if (!EXPECT(excluded_segs, TRUE)) {
        GC_exclude_static_roots_inner((ptr_t)load_segs,
                                      (ptr_t)load_segs + sizeof(load_segs));
        excluded_segs = TRUE;
      }
    }
# endif

  did_something = 0;
  dl_iterate_phdr(GC_register_dynlib_callback, &did_something);
  if (did_something) {
#   ifdef PT_GNU_RELRO
      int i;

      for (i = 0; i < n_load_segs; ++i) {
        if (ADDR_LT(load_segs[i].start, load_segs[i].end))
          GC_add_roots_inner(load_segs[i].start, load_segs[i].end, TRUE);
        if (ADDR_LT(load_segs[i].start2, load_segs[i].end2))
          GC_add_roots_inner(load_segs[i].start2, load_segs[i].end2, TRUE);
      }
#   endif
  } else {
      ptr_t datastart, dataend;
#     ifdef DATASTART_IS_FUNC
        static ptr_t datastart_cached = MAKE_CPTR(GC_WORD_MAX);

        /* Evaluate DATASTART only once.  */
        if (ADDR(datastart_cached) == GC_WORD_MAX) {
          datastart_cached = DATASTART;
        }
        datastart = datastart_cached;
#     else
        datastart = DATASTART;
#     endif
#     ifdef DATAEND_IS_FUNC
        {
          static ptr_t dataend_cached = 0;
          /* Evaluate DATAEND only once. */
          if (dataend_cached == 0) {
            dataend_cached = DATAEND;
          }
          dataend = dataend_cached;
        }
#     else
        dataend = DATAEND;
#     endif
      if (NULL == *(char * volatile *)&datastart
          || ADDR_LT(dataend, datastart))
        ABORT_ARG2("Wrong DATASTART/END pair",
                   ": %p .. %p", (void *)datastart, (void *)dataend);

      /* dl_iterate_phdr may forget the static data segment in  */
      /* statically linked executables.                         */
      GC_add_roots_inner(datastart, dataend, TRUE);
#     ifdef GC_HAVE_DATAREGION2
        if (ADDR(DATASTART2) - 1U >= ADDR(DATAEND2)) {
                        /* Subtract one to check also for NULL  */
                        /* without a compiler warning.          */
          ABORT_ARG2("Wrong DATASTART/END2 pair",
                     ": %p .. %p", (void *)DATASTART2, (void *)DATAEND2);
        }
        GC_add_roots_inner(DATASTART2, DATAEND2, TRUE);
#     endif
  }
  return TRUE;
}

# define HAVE_REGISTER_MAIN_STATIC_DATA

#else /* !HAVE_DL_ITERATE_PHDR */

/* Dynamic loading code for Linux running ELF. Somewhat tested on
 * Linux/i686, untested but hopefully should work on Linux/Alpha.
 * This code was derived from the Solaris/ELF support. Thanks to
 * whatever kind soul wrote that.  - Patrick Bridges */

/* This doesn't necessarily work in all cases, e.g. with preloaded
 * dynamic libraries.                                           */

# if defined(NETBSD) || defined(OPENBSD)
#   include <sys/exec_elf.h>
   /* for compatibility with 1.4.x */
#   ifndef DT_DEBUG
#     define DT_DEBUG   21
#   endif
#   ifndef PT_LOAD
#     define PT_LOAD    1
#   endif
#   ifndef PF_W
#     define PF_W       2
#   endif
# elif !defined(HOST_ANDROID)
#   include <elf.h>
# endif

# ifndef HOST_ANDROID
#   include <link.h>
# endif

#endif /* !HAVE_DL_ITERATE_PHDR */

EXTERN_C_BEGIN
#ifdef __GNUC__
# pragma weak _DYNAMIC
#endif
extern ElfW(Dyn) _DYNAMIC[];
EXTERN_C_END

STATIC struct link_map *
GC_FirstDLOpenedLinkMap(void)
{
    static struct link_map *cachedResult = 0;

    if (0 == COVERT_DATAFLOW(ADDR(_DYNAMIC))) {
        /* _DYNAMIC symbol not resolved. */
        return NULL;
    }
    if (NULL == cachedResult) {
#     if defined(NETBSD) && defined(RTLD_DI_LINKMAP)
#       if defined(CPPCHECK)
#         define GC_RTLD_DI_LINKMAP 2
#       else
#         define GC_RTLD_DI_LINKMAP RTLD_DI_LINKMAP
#       endif
        struct link_map *lm = NULL;
        if (!dlinfo(RTLD_SELF, GC_RTLD_DI_LINKMAP, &lm) && lm != NULL) {
            /* Now lm points link_map object of libgc.  Since it    */
            /* might not be the first dynamically linked object,    */
            /* try to find it (object next to the main object).     */
            while (lm->l_prev != NULL) {
                lm = lm->l_prev;
            }
            cachedResult = lm->l_next;
        }
#     else
        ElfW(Dyn) *dp;
        int tag;

        for (dp = _DYNAMIC; (tag = dp->d_tag) != 0; dp++) {
            if (tag == DT_DEBUG) {
                const struct r_debug *rd = (struct r_debug *)dp->d_un.d_ptr;
                /* d_ptr could be null if libs are linked statically. */
                if (rd != NULL) {
                    const struct link_map *lm = rd->r_map;
                    if (lm != NULL)
                        cachedResult = lm->l_next; /* might be NULL */
                }
                break;
            }
        }
#     endif /* !NETBSD || !RTLD_DI_LINKMAP */
    }
    return cachedResult;
}

GC_INNER void GC_register_dynamic_libraries(void)
{
  struct link_map *lm;

  GC_ASSERT(I_HOLD_LOCK());
# ifdef HAVE_DL_ITERATE_PHDR
    if (GC_register_dynamic_libraries_dl_iterate_phdr()) {
        return;
    }
# endif
  for (lm = GC_FirstDLOpenedLinkMap(); lm != 0; lm = lm->l_next)
    {
        ElfW(Ehdr) * e;
        ElfW(Phdr) * p;
        unsigned long offset;
        char * start;
        int i;

        e = (ElfW(Ehdr) *)lm->l_addr;
#       ifdef HOST_ANDROID
          if (e == NULL)
            continue;
#       endif
        p = ((ElfW(Phdr) *)(((char *)(e)) + e->e_phoff));
        offset = ((unsigned long)(lm->l_addr));
        for (i = 0; i < (int)e->e_phnum; i++, p++) {
          switch (p->p_type) {
            case PT_LOAD:
              if (!(p->p_flags & PF_W)) break;
              start = (char *)(p->p_vaddr) + offset;
              GC_add_roots_inner(start, start + p->p_memsz, TRUE);
              break;
            default:
              break;
          }
        }
#       if defined(CPPCHECK) && defined(HOST_ANDROID) \
           && !defined(GC_DONT_DEFINE_LINK_MAP) && !(__ANDROID_API__ >= 21)
          GC_noop1_ptr(lm -> l_name);
          GC_noop1((word)(lm -> l_ld));
          GC_noop1_ptr(lm -> l_prev);
#       endif
    }
}

#endif /* !USE_PROC_FOR_LIBRARIES */

#endif /* LINUX */

#if defined(IRIX5) || (defined(USE_PROC_FOR_LIBRARIES) && !defined(LINUX))

#include <sys/procfs.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <elf.h>
#include <errno.h>
#include <signal.h>  /* Only for the following test. */
#ifndef _sigargs
# define IRIX6
#endif

/* We use /proc to track down all parts of the address space that are   */
/* mapped by the process, and throw out regions we know we shouldn't    */
/* worry about.  This may also work under other SVR4 variants.          */
GC_INNER void GC_register_dynamic_libraries(void)
{
    static int fd = -1;
    static prmap_t * addr_map = 0;
    static int current_sz = 0;  /* Number of records currently in addr_map */

    char buf[32];
    int needed_sz = 0;          /* Required size of addr_map            */
    int i;
    long flags;
    ptr_t start;
    ptr_t limit;
    word heap_start = ADDR(HEAP_START);
    word heap_end = heap_start;

#   ifdef SOLARISDL
#     define MA_PHYS 0
#   endif /* SOLARISDL */

    GC_ASSERT(I_HOLD_LOCK());
    if (fd < 0) {
      (void)snprintf(buf, sizeof(buf), "/proc/%ld", (long)getpid());
      buf[sizeof(buf) - 1] = '\0';
      fd = open(buf, O_RDONLY);
      if (fd < 0) {
        ABORT("/proc open failed");
      }
    }
    if (ioctl(fd, PIOCNMAP, &needed_sz) < 0) {
        ABORT_ARG2("/proc PIOCNMAP ioctl failed",
                   ": fd= %d, errno= %d", fd, errno);
    }
    if (needed_sz >= current_sz) {
        GC_scratch_recycle_no_gww(addr_map,
                                  (size_t)current_sz * sizeof(prmap_t));
        current_sz = needed_sz * 2 + 1;
                        /* Expansion, plus room for 0 record */
        addr_map = (prmap_t *)GC_scratch_alloc(
                                (size_t)current_sz * sizeof(prmap_t));
        if (addr_map == NULL)
          ABORT("Insufficient memory for address map");
    }
    if (ioctl(fd, PIOCMAP, addr_map) < 0) {
        ABORT_ARG3("/proc PIOCMAP ioctl failed",
                   ": errcode= %d, needed_sz= %d, addr_map= %p",
                   errno, needed_sz, (void *)addr_map);
    }
    if (GC_n_heap_sects > 0) {
        heap_end = ADDR(GC_heap_sects[GC_n_heap_sects-1].hs_start)
                        + GC_heap_sects[GC_n_heap_sects-1].hs_bytes;
        if (heap_end < GC_scratch_last_end_addr)
          heap_end = GC_scratch_last_end_addr;
    }
    for (i = 0; i < needed_sz; i++) {
        flags = addr_map[i].pr_mflags;
        if ((flags & (MA_BREAK | MA_STACK | MA_PHYS
                      | MA_FETCHOP | MA_NOTCACHED)) != 0) goto irrelevant;
        if ((flags & (MA_READ | MA_WRITE)) != (MA_READ | MA_WRITE))
            goto irrelevant;
          /* The latter test is empirically useless in very old Irix    */
          /* versions.  Other than the                                  */
          /* main data and stack segments, everything appears to be     */
          /* mapped readable, writable, executable, and shared(!!).     */
          /* This makes no sense to me. - HB                            */
        start = (ptr_t)(addr_map[i].pr_vaddr);
        if (GC_roots_present(start)
            || (ADDR(start) >= heap_start && ADDR(start) < heap_end))
          goto irrelevant;

        limit = start + addr_map[i].pr_size;
        /* The following seemed to be necessary for very old versions   */
        /* of Irix, but it has been reported to discard relevant        */
        /* segments under Irix 6.5.                                     */
#       ifndef IRIX6
          if (addr_map[i].pr_off == 0 && strncmp(start, ELFMAG, 4) == 0) {
            /* Discard text segments, i.e. 0-offset mappings against    */
            /* executable files which appear to have ELF headers.       */
            caddr_t arg;
            int obj;
#           define MAP_IRR_SZ 10
            static ptr_t map_irr[MAP_IRR_SZ];
                                        /* Known irrelevant map entries */
            static int n_irr = 0;
            struct stat buf;
            int j;

            for (j = 0; j < n_irr; j++) {
                if (map_irr[j] == start) goto irrelevant;
            }
            arg = (caddr_t)start;
            obj = ioctl(fd, PIOCOPENM, &arg);
            if (obj >= 0) {
                fstat(obj, &buf);
                close(obj);
                if ((buf.st_mode & 0111) != 0) {
                    if (n_irr < MAP_IRR_SZ) {
                        map_irr[n_irr++] = start;
                    }
                    goto irrelevant;
                }
            }
          }
#       endif /* !IRIX6 */
        GC_add_roots_inner(start, limit, TRUE);
      irrelevant: ;
    }
    /* Don't keep cached descriptor, for now.  Some kernels don't like us */
    /* to keep a /proc file descriptor around during kill -9.             */
    /* Otherwise, it should also require FD_CLOEXEC and proper handling   */
    /* at fork (i.e. close because of the pid change).                    */
        if (close(fd) < 0) ABORT("Couldn't close /proc file");
        fd = -1;
}

# endif /* USE_PROC_FOR_LIBRARIES || IRIX5 */

#ifdef ANY_MSWIN
  /* We traverse the entire address space and register all segments     */
  /* that could possibly have been written to.                          */
  STATIC void GC_cond_add_roots(ptr_t base, ptr_t limit)
  {
#   ifdef THREADS
      ptr_t curr_base = base;
      ptr_t next_stack_lo, next_stack_hi;
#   else
      ptr_t stack_top;
#   endif

    GC_ASSERT(I_HOLD_LOCK());
    if (base == limit) return;
#   ifdef THREADS
      for (;;) {
          GC_get_next_stack(curr_base, limit, &next_stack_lo, &next_stack_hi);
          if (ADDR_GE(next_stack_lo, limit)) break;
          if (ADDR_LT(curr_base, next_stack_lo))
            GC_add_roots_inner(curr_base, next_stack_lo, TRUE);
          curr_base = next_stack_hi;
      }
      if (ADDR_LT(curr_base, limit))
        GC_add_roots_inner(curr_base, limit, TRUE);
#   else
      stack_top = PTR_ALIGN_DOWN(GC_approx_sp(),
                                 GC_sysinfo.dwAllocationGranularity);
      if (ADDR_LT(stack_top, limit) && ADDR_LT(base, GC_stackbottom)) {
          /* Part of the stack; ignore it. */
          return;
      }
      GC_add_roots_inner(base, limit, TRUE);
#   endif
  }

#ifdef DYNAMIC_LOADING
  /* GC_register_main_static_data is not needed unless DYNAMIC_LOADING. */
  GC_INNER GC_bool GC_register_main_static_data(void)
  {
#   if defined(MSWINCE) || defined(CYGWIN32)
      /* Do we need to separately register the main static data segment? */
      return FALSE;
#   else
      return GC_no_win32_dlls;
#   endif
  }
# define HAVE_REGISTER_MAIN_STATIC_DATA
#endif /* DYNAMIC_LOADING */

# ifdef DEBUG_VIRTUALQUERY
  void GC_dump_meminfo(MEMORY_BASIC_INFORMATION *buf)
  {
    GC_printf("BaseAddress= 0x%lx, AllocationBase= 0x%lx,"
              " RegionSize= 0x%lx(%lu)\n",
              buf -> BaseAddress, buf -> AllocationBase,
              buf -> RegionSize, buf -> RegionSize);
    GC_printf("\tAllocationProtect= 0x%lx, State= 0x%lx, Protect= 0x%lx, "
              "Type= 0x%lx\n", buf -> AllocationProtect, buf -> State,
              buf -> Protect, buf -> Type);
  }
# endif /* DEBUG_VIRTUALQUERY */

# if defined(MSWINCE) || defined(CYGWIN32)
    /* FIXME: Should we really need to scan MEM_PRIVATE sections?       */
    /* For now, we don't add MEM_PRIVATE sections to the data roots for */
    /* WinCE because otherwise SEGV fault sometimes happens to occur in */
    /* GC_mark_from() (and, even if we use WRAP_MARK_SOME, WinCE prints */
    /* a "Data Abort" message to the debugging console).                */
    /* To workaround that, use -DGC_REGISTER_MEM_PRIVATE.               */
#   define GC_wnt TRUE
# endif

  GC_INNER void GC_register_dynamic_libraries(void)
  {
    ptr_t p, base, limit;

    GC_ASSERT(I_HOLD_LOCK());
#   ifdef MSWIN32
      if (GC_no_win32_dlls) return;
#   endif
    p = (ptr_t)GC_sysinfo.lpMinimumApplicationAddress;
    base = limit = p;
    while (ADDR_LT(p, (ptr_t)GC_sysinfo.lpMaximumApplicationAddress)) {
      MEMORY_BASIC_INFORMATION buf;
      size_t result = VirtualQuery((LPVOID)p, &buf, sizeof(buf));

#     ifdef MSWINCE
        if (0 == result) {
          if (ADDR(p) > GC_WORD_MAX - GC_sysinfo.dwAllocationGranularity)
            break; /* overflow */
          /* Page is free; advance to the next possible allocation base. */
          p = PTR_ALIGN_UP(p + 1, GC_sysinfo.dwAllocationGranularity);
        } else
#     endif
      /* else */ {
        DWORD protect;

        if (result != sizeof(buf))
          ABORT("Weird VirtualQuery result");
        if (ADDR(p) > GC_WORD_MAX - buf.RegionSize) break; /* overflow */

        protect = buf.Protect;
        if (buf.State == MEM_COMMIT
            && (protect == PAGE_EXECUTE_READWRITE
                || protect == PAGE_EXECUTE_WRITECOPY
                || protect == PAGE_READWRITE
                || protect == PAGE_WRITECOPY)
            && (buf.Type == MEM_IMAGE
#               ifdef GC_REGISTER_MEM_PRIVATE
                  || (protect == PAGE_READWRITE && buf.Type == MEM_PRIVATE)
#               else
                  /* There is some evidence that we cannot always   */
                  /* ignore MEM_PRIVATE sections under Windows ME   */
                  /* and predecessors.  Hence we now also check for */
                  /* that case.                                     */
                  || (!GC_wnt && buf.Type == MEM_PRIVATE)
#               endif
               )
            && !GC_is_heap_base(buf.AllocationBase)) {
#         ifdef DEBUG_VIRTUALQUERY
            GC_dump_meminfo(&buf);
#         endif
          if (p != limit) {
            GC_cond_add_roots(base, limit);
            base = p;
          }
          limit = p + buf.RegionSize;
        }
        p += buf.RegionSize;
      }
    }
    GC_cond_add_roots(base, limit);
  }
#endif /* ANY_MSWIN */

#if defined(ALPHA) && defined(OSF1)
# include <loader.h>

  EXTERN_C_BEGIN
  extern char *sys_errlist[];
  extern int sys_nerr;
  extern int errno;
  EXTERN_C_END

  GC_INNER void GC_register_dynamic_libraries(void)
  {
    ldr_module_t moduleid = LDR_NULL_MODULE;
    ldr_process_t mypid;

    GC_ASSERT(I_HOLD_LOCK());
    mypid = ldr_my_process(); /* obtain id of this process */

    /* For each module. */
    for (;;) {
      ldr_module_info_t moduleinfo;
      size_t modulereturnsize;
      ldr_region_t region;
      ldr_region_info_t regioninfo;
      size_t regionreturnsize;
      int status = ldr_next_module(mypid, &moduleid);
                                /* Get the next (first) module */

      if (moduleid == LDR_NULL_MODULE)
        break;  /* no more modules */

      /* Check status AFTER checking moduleid because       */
      /* of a bug in the non-shared ldr_next_module stub.   */
        if (status != 0) {
          ABORT_ARG3("ldr_next_module failed",
                     ": status= %d, errcode= %d (%s)", status, errno,
                     errno < sys_nerr ? sys_errlist[errno] : "");
        }

      /* Get the module information */
        status = ldr_inq_module(mypid, moduleid, &moduleinfo,
                                sizeof(moduleinfo), &modulereturnsize);
        if (status != 0 )
            ABORT("ldr_inq_module failed");

      /* is module for the main program (i.e. nonshared portion)? */
          if (moduleinfo.lmi_flags & LDR_MAIN)
              continue;    /* skip the main module */

#     ifdef DL_VERBOSE
        GC_log_printf("---Module---\n");
        GC_log_printf("Module ID: %ld\n", moduleinfo.lmi_modid);
        GC_log_printf("Count of regions: %d\n", moduleinfo.lmi_nregion);
        GC_log_printf("Flags for module: %016lx\n", moduleinfo.lmi_flags);
        GC_log_printf("Module pathname: \"%s\"\n", moduleinfo.lmi_name);
#     endif

      /* For each region in this module. */
        for (region = 0; region < moduleinfo.lmi_nregion; region++) {
          /* Get the region information */
            status = ldr_inq_region(mypid, moduleid, region, &regioninfo,
                                    sizeof(regioninfo), &regionreturnsize);
            if (status != 0 )
                ABORT("ldr_inq_region failed");

          /* only process writable (data) regions */
            if (! (regioninfo.lri_prot & LDR_W))
                continue;

#         ifdef DL_VERBOSE
            GC_log_printf("--- Region ---\n");
            GC_log_printf("Region number: %ld\n", regioninfo.lri_region_no);
            GC_log_printf("Protection flags: %016x\n", regioninfo.lri_prot);
            GC_log_printf("Virtual address: %p\n", regioninfo.lri_vaddr);
            GC_log_printf("Mapped address: %p\n", regioninfo.lri_mapaddr);
            GC_log_printf("Region size: %ld\n", regioninfo.lri_size);
            GC_log_printf("Region name: \"%s\"\n", regioninfo.lri_name);
#         endif

          /* register region as a garbage collection root */
          GC_add_roots_inner((char *)regioninfo.lri_mapaddr,
                        (char *)regioninfo.lri_mapaddr + regioninfo.lri_size,
                        TRUE);

        }
    }
  }
#endif /* ALPHA && OSF1 */

#if defined(HPUX)
#include <errno.h>
#include <dl.h>

EXTERN_C_BEGIN
extern char *sys_errlist[];
extern int sys_nerr;
EXTERN_C_END

GC_INNER void GC_register_dynamic_libraries(void)
{
  int index = 1; /* Ordinal position in shared library search list */

  GC_ASSERT(I_HOLD_LOCK());
  /* For each dynamic library loaded. */
  for (;;) {
      struct shl_descriptor *shl_desc; /* Shared library info, see dl.h */
      int status = shl_get(index, &shl_desc);
                                /* Get info about next shared library   */

      /* Check if this is the end of the list or if some error occurred */
        if (status != 0) {
#        ifdef GC_HPUX_THREADS
           /* I've seen errno values of 0.  The man page is not clear   */
           /* as to whether errno should get set on a -1 return.        */
           break;
#        else
          if (errno == EINVAL) {
            break; /* Moved past end of shared library list --> finished */
          } else {
            ABORT_ARG3("shl_get failed",
                       ": status= %d, errcode= %d (%s)", status, errno,
                       errno < sys_nerr ? sys_errlist[errno] : "");
          }
#        endif
        }

#     ifdef DL_VERBOSE
        GC_log_printf("---Shared library---\n");
        GC_log_printf("filename= \"%s\"\n", shl_desc->filename);
        GC_log_printf("index= %d\n", index);
        GC_log_printf("handle= %08x\n", (unsigned long) shl_desc->handle);
        GC_log_printf("text seg.start= %08x\n", shl_desc->tstart);
        GC_log_printf("text seg.end= %08x\n", shl_desc->tend);
        GC_log_printf("data seg.start= %08x\n", shl_desc->dstart);
        GC_log_printf("data seg.end= %08x\n", shl_desc->dend);
        GC_log_printf("ref.count= %lu\n", shl_desc->ref_count);
#     endif

      /* register shared library's data segment as a garbage collection root */
        GC_add_roots_inner((char *) shl_desc->dstart,
                           (char *) shl_desc->dend, TRUE);

        index++;
  }
}
#endif /* HPUX */

#ifdef AIX
# include <alloca.h>
# include <sys/ldr.h>
# include <sys/errno.h>

  GC_INNER void GC_register_dynamic_libraries(void)
  {
      int ldibuflen = 8192;

      GC_ASSERT(I_HOLD_LOCK());
      for (;;) {
        int len;
        struct ld_info *ldi;
#       if defined(CPPCHECK)
          char ldibuf[ldibuflen];
#       else
          char *ldibuf = alloca(ldibuflen);
#       endif

        len = loadquery(L_GETINFO, ldibuf, ldibuflen);
        if (len < 0) {
                if (errno != ENOMEM) {
                        ABORT("loadquery failed");
                }
                ldibuflen *= 2;
                continue;
        }

        ldi = (struct ld_info *)ldibuf;
        while (ldi) {
                len = ldi->ldinfo_next;
                GC_add_roots_inner(
                                ldi->ldinfo_dataorg,
                                (ptr_t)(unsigned long)ldi->ldinfo_dataorg
                                + ldi->ldinfo_datasize,
                                TRUE);
                ldi = len ? (struct ld_info *)((char *)ldi + len) : 0;
        }
        break;
      }
  }
#endif /* AIX */

#ifdef DARWIN

/* __private_extern__ hack required for pre-3.4 gcc versions.   */
#ifndef __private_extern__
# define __private_extern__ extern
# include <mach-o/dyld.h>
# undef __private_extern__
#else
# include <mach-o/dyld.h>
#endif

#if CPP_WORDSZ == 64
# define GC_MACH_HEADER mach_header_64
#else
# define GC_MACH_HEADER mach_header
#endif

#ifdef MISSING_MACH_O_GETSECT_H
  EXTERN_C_BEGIN
  extern uint8_t *getsectiondata(const struct GC_MACH_HEADER *,
                    const char *seg, const char *sect, unsigned long *psz);
  EXTERN_C_END
#else
# include <mach-o/getsect.h>
#endif

/*#define DARWIN_DEBUG*/

/* Writable sections generally available on Darwin.     */
STATIC const struct dyld_sections_s {
    const char *seg;
    const char *sect;
} GC_dyld_sections[] = {
    { SEG_DATA, SECT_DATA },
    /* Used by FSF GCC, but not by OS X system tools, so far.   */
    { SEG_DATA, "__static_data" },
    { SEG_DATA, SECT_BSS },
    { SEG_DATA, SECT_COMMON },
    /* FSF GCC - zero-sized object sections for targets         */
    /*supporting section anchors.                               */
    { SEG_DATA, "__zobj_data" },
    { SEG_DATA, "__zobj_bss" }
};

/* Additional writable sections:                                */
/* GCC on Darwin constructs aligned sections "on demand", where */
/* the alignment size is embedded in the section name.          */
/* Furthermore, there are distinctions between sections         */
/* containing private vs. public symbols.  It also constructs   */
/* sections specifically for zero-sized objects, when the       */
/* target supports section anchors.                             */
STATIC const char * const GC_dyld_bss_prefixes[] = {
  "__bss",
  "__pu_bss",
  "__zo_bss",
  "__zo_pu_bss"
};

/* Currently, mach-o will allow up to the max of 2^15 alignment */
/* in an object file.                                           */
#ifndef L2_MAX_OFILE_ALIGNMENT
# define L2_MAX_OFILE_ALIGNMENT 15
#endif

STATIC const char *GC_dyld_name_for_hdr(const struct GC_MACH_HEADER *phdr)
{
    unsigned long i, count = _dyld_image_count();

    for (i = 0; i < count; i++) {
      if ((const struct GC_MACH_HEADER *)_dyld_get_image_header(i) == phdr)
        return _dyld_get_image_name(i);
    }
    /* TODO: probably ABORT in this case? */
    return NULL; /* not found */
}

/* getsectbynamefromheader is deprecated (first time in macOS 13.0),    */
/* getsectiondata (introduced in macOS 10.7) is used instead if exists. */
/* Define USE_GETSECTBYNAME to use the deprecated symbol, if needed.    */
#if !defined(USE_GETSECTBYNAME) \
    && (MAC_OS_X_VERSION_MIN_REQUIRED < 1070 /*MAC_OS_X_VERSION_10_7*/)
# define USE_GETSECTBYNAME
#endif

static void dyld_section_add_del(const struct GC_MACH_HEADER *phdr,
                                 intptr_t slide, const char *dlpi_name,
                                 GC_has_static_roots_func callback,
                                 const char *seg, const char *secnam,
                                 GC_bool is_add)
{
  unsigned long start, end, sec_size;
# ifdef USE_GETSECTBYNAME
#   if CPP_WORDSZ == 64
      const struct section_64 *sec = getsectbynamefromheader_64(phdr, seg,
                                                                secnam);
#   else
      const struct section *sec = getsectbynamefromheader(phdr, seg, secnam);
#   endif

    if (NULL == sec) return;
    sec_size = sec -> size;
    start = slide + sec -> addr;
# else

    UNUSED_ARG(slide);
    sec_size = 0;
    start = (unsigned long)getsectiondata(phdr, seg, secnam, &sec_size);
    if (0 == start) return;
# endif
  if (sec_size < sizeof(ptr_t)) return;
  end = start + sec_size;
  if (is_add) {
    LOCK();
    /* The user callback is invoked holding the allocator lock.   */
    if (EXPECT(callback != 0, FALSE)
        && !callback(dlpi_name, (void *)start, (size_t)sec_size)) {
      UNLOCK();
      return; /* skip section */
    }
    GC_add_roots_inner((ptr_t)start, (ptr_t)end, FALSE);
    UNLOCK();
  } else {
    GC_remove_roots((void *)start, (void *)end);
  }
# ifdef DARWIN_DEBUG
    GC_log_printf("%s section __DATA,%s at %p-%p (%lu bytes) from image %s\n",
                  is_add ? "Added" : "Removed",
                  secnam, (void *)start, (void *)end, sec_size, dlpi_name);
# endif
}

static void dyld_image_add_del(const struct GC_MACH_HEADER *phdr,
                               intptr_t slide,
                               GC_has_static_roots_func callback,
                               GC_bool is_add)
{
  unsigned i, j;
  const char *dlpi_name;

  GC_ASSERT(I_DONT_HOLD_LOCK());
# ifndef DARWIN_DEBUG
    if (0 == callback) {
      dlpi_name = NULL;
    } else
# endif
  /* else */ {
    dlpi_name = GC_dyld_name_for_hdr(phdr);
  }
  for (i = 0; i < sizeof(GC_dyld_sections)/sizeof(GC_dyld_sections[0]); i++) {
    dyld_section_add_del(phdr, slide, dlpi_name, callback,
                         GC_dyld_sections[i].seg, GC_dyld_sections[i].sect,
                         is_add);
  }

  /* Sections constructed on demand.    */
  for (j = 0; j < sizeof(GC_dyld_bss_prefixes) / sizeof(char *); j++) {
    /* Our manufactured aligned BSS sections.   */
    for (i = 0; i <= L2_MAX_OFILE_ALIGNMENT; i++) {
      char secnam[16];

      (void)snprintf(secnam, sizeof(secnam), "%s%u",
                     GC_dyld_bss_prefixes[j], i);
      secnam[sizeof(secnam) - 1] = '\0';
      dyld_section_add_del(phdr, slide, dlpi_name, 0 /* callback */, SEG_DATA,
                           secnam, is_add);
    }
  }

# if defined(DARWIN_DEBUG) && !defined(NO_DEBUGGING)
    READER_LOCK();
    GC_print_static_roots();
    READER_UNLOCK();
# endif
}

STATIC void GC_dyld_image_add(const struct GC_MACH_HEADER *phdr,
                              intptr_t slide)
{
  if (!GC_no_dls)
    dyld_image_add_del(phdr, slide, GC_has_static_roots, TRUE);
}

STATIC void GC_dyld_image_remove(const struct GC_MACH_HEADER *phdr,
                                 intptr_t slide)
{
  dyld_image_add_del(phdr, slide, 0 /* callback */, FALSE);
}

GC_INNER void GC_register_dynamic_libraries(void)
{
    /* Currently does nothing. The callbacks are setup by GC_init_dyld()
    The dyld library takes it from there. */
}

/* The _dyld_* functions have an internal lock, so none of them can be  */
/* called while the world is stopped without the risk of a deadlock.    */
/* Because of this we MUST setup callbacks BEFORE we ever stop the      */
/* world.  This should be called BEFORE any thread is created and       */
/* WITHOUT the allocator lock held.                                     */

/* _dyld_bind_fully_image_containing_address is deprecated, so use      */
/* dlopen(0,RTLD_NOW) instead; define USE_DYLD_TO_BIND to override this */
/* if needed.                                                           */

GC_INNER void GC_init_dyld(void)
{
  static GC_bool initialized = FALSE;

  GC_ASSERT(I_DONT_HOLD_LOCK());
  if (initialized) return;

# ifdef DARWIN_DEBUG
    GC_log_printf("Registering dyld callbacks...\n");
# endif

  /* Apple's Documentation:
     When you call _dyld_register_func_for_add_image, the dynamic linker
     runtime calls the specified callback (func) once for each of the images
     that is currently loaded into the program. When a new image is added to
     the program, your callback is called again with the mach_header for the
     new image, and the virtual memory slide amount of the new image.

     This WILL properly register already linked libraries and libraries
     linked in the future.
  */
  _dyld_register_func_for_add_image(
        (void (*)(const struct mach_header*, intptr_t))GC_dyld_image_add);
  _dyld_register_func_for_remove_image(
        (void (*)(const struct mach_header*, intptr_t))GC_dyld_image_remove);
                        /* Structure mach_header_64 has the same fields */
                        /* as mach_header except for the reserved one   */
                        /* at the end, so these casts are OK.           */

  /* Set this early to avoid reentrancy issues. */
  initialized = TRUE;

# ifndef NO_DYLD_BIND_FULLY_IMAGE
    if (GC_no_dls) return; /* skip main data segment registration */

    /* When the environment variable is set, the dynamic linker binds   */
    /* all undefined symbols the application needs at launch time.      */
    /* This includes function symbols that are normally bound lazily at */
    /* the time of their first invocation.                              */
    if (GETENV("DYLD_BIND_AT_LAUNCH") != NULL) return;

    /* The environment variable is unset, so we should bind manually.   */
#   ifdef DARWIN_DEBUG
      GC_log_printf("Forcing full bind of GC code...\n");
#   endif
#   ifndef USE_DYLD_TO_BIND
      {
        void *dl_handle = dlopen(NULL, RTLD_NOW);

        if (!dl_handle)
          ABORT("dlopen failed (to bind fully image)");
        /* Note that the handle is never closed.        */
#       if defined(CPPCHECK) || defined(LINT2)
          GC_noop1_ptr(dl_handle);
#       endif
      }
#   else
      /* Note: '_dyld_bind_fully_image_containing_address' is deprecated. */
      if (!_dyld_bind_fully_image_containing_address(
                                                  (unsigned long *)GC_malloc))
        ABORT("_dyld_bind_fully_image_containing_address failed");
#   endif
# endif
}

#define HAVE_REGISTER_MAIN_STATIC_DATA
GC_INNER GC_bool GC_register_main_static_data(void)
{
  /* Already done through dyld callbacks */
  return FALSE;
}

#endif /* DARWIN */

#if defined(HAIKU)
# include <kernel/image.h>

  GC_INNER void GC_register_dynamic_libraries(void)
  {
    image_info info;
    int32 cookie = 0;

    GC_ASSERT(I_HOLD_LOCK());
    while (get_next_image_info(0, &cookie, &info) == B_OK) {
      ptr_t data = (ptr_t)info.data;
      GC_add_roots_inner(data, data + info.data_size, TRUE);
    }
  }
#endif /* HAIKU */

#elif defined(PCR)

# include "il/PCR_IL.h"
# include "th/PCR_ThCtl.h"
# include "mm/PCR_MM.h"

  GC_INNER void GC_register_dynamic_libraries(void)
  {
    /* Add new static data areas of dynamically loaded modules. */
    const PCR_IL_LoadedFile * p = PCR_IL_GetLastLoadedFile();
    PCR_IL_LoadedSegment * q;

    /* Skip uncommitted files */
    while (p != NIL && !(p -> lf_commitPoint)) {
        /* The loading of this file has not yet been committed    */
        /* Hence its description could be inconsistent.           */
        /* Furthermore, it hasn't yet been run.  Hence its data   */
        /* segments can't possibly reference heap allocated       */
        /* objects.                                               */
        p = p -> lf_prev;
    }
    for (; p != NIL; p = p -> lf_prev) {
      for (q = p -> lf_ls; q != NIL; q = q -> ls_next) {
        if ((q -> ls_flags & PCR_IL_SegFlags_Traced_MASK)
            == PCR_IL_SegFlags_Traced_on) {
          GC_add_roots_inner((ptr_t)q->ls_addr,
                             (ptr_t)q->ls_addr + q->ls_bytes, TRUE);
        }
      }
    }
  }

#endif /* PCR && !ANY_MSWIN */

#ifdef GC_MUST_RESTORE_REDEFINED_DLOPEN
# define dlopen GC_dlopen
#endif

#if !defined(HAVE_REGISTER_MAIN_STATIC_DATA) && defined(DYNAMIC_LOADING)
  /* Do we need to separately register the main static data segment? */
  GC_INNER GC_bool GC_register_main_static_data(void)
  {
    return TRUE;
  }
#endif /* HAVE_REGISTER_MAIN_STATIC_DATA */

/* Register a routine to filter dynamic library registration.  */
GC_API void GC_CALL GC_register_has_static_roots_callback(
                                        GC_has_static_roots_func callback)
{
    GC_has_static_roots = callback;
}
